TobyCoulson Posted September 11, 2012 Share Posted September 11, 2012 If I choose to replace my 15" wheels with 13" ones will I need to change much? I gather the smaller rim is better to drive. Apologies for being an idiot. Link to comment Share on other sites More sharing options...
johnv Posted September 11, 2012 Share Posted September 11, 2012 tyres? Link to comment Share on other sites More sharing options...
TobyCoulson Posted September 11, 2012 Author Share Posted September 11, 2012 CR500 Link to comment Share on other sites More sharing options...
Grandmaster Flatcap Posted September 11, 2012 Share Posted September 11, 2012 Speedo reading? Link to comment Share on other sites More sharing options...
TobyCoulson Posted September 11, 2012 Author Share Posted September 11, 2012 I can see this is not going to be an easy transition. I was hoping I could replace my 15" rims with 13" ones but with the same overall diameter. Link to comment Share on other sites More sharing options...
johnv Posted September 11, 2012 Share Posted September 11, 2012 I have a spare set of 13's with CR500's if you want to try them out you're welcome Link to comment Share on other sites More sharing options...
Roger Ford Posted September 11, 2012 Share Posted September 11, 2012 What are the tyres on the 15 inch rim? Use a tyre calculator like this one to see how much change (if any) there will be with new tyres. CR500 probably aren't the best choice as they're fairly low profile. You may find with A048R, for example, that the sizes are very similar. Link to comment Share on other sites More sharing options...
Z3MCJez Posted September 11, 2012 Share Posted September 11, 2012 I think the speedo reprogramming is fairly straightforward. If you do change rolling diameter you'll want to change ride height to compensate. You will then think that your wing stays look like they're miles from the tyres, and may want to consider lower profile wing stays. Which may necessitate new cycle wings. Depends on how much you want to do! Why not try with some borrowed wheels/tyres (wind all platforms up or down by an equal amount to compensate for different tyres, which won't be perfect but will be better than doing nothing) and see what you think before you sink a grand in wheels/tyres/accessories. Jez Link to comment Share on other sites More sharing options...
kenny. Posted September 11, 2012 Share Posted September 11, 2012 As Roger said....... on my last 7 I switched between 16s and 13s with 888s............diameter difference was not massive and looks were still OK............it does look a bit naff with 13s if you have the long cycle wings though. Link to comment Share on other sites More sharing options...
Alan Bowler Posted September 11, 2012 Share Posted September 11, 2012 Toby, I've got a set of silver minilite 13s in Claygate with 60 profile A539 tyres on you are welcome to borrow, and pose around Cobham in to see how many admiring glances you get. Not the grippiest of tyre, but 13" A048s/Toyo 888s are typically 60 profile as well. AB Link to comment Share on other sites More sharing options...
Ozzy Posted September 11, 2012 Share Posted September 11, 2012 I know I'm thick, but I've just been playing with Roger's tyre calculator, and why does the tyre width make a difference to the diameter? I'd have thought wheel size & profile would determine this. What am I missing? Oz. Link to comment Share on other sites More sharing options...
kenny. Posted September 11, 2012 Share Posted September 11, 2012 Ozzy, because the profile is a percentage of the width...........so a 60 series 225 is a bigger profile than a 60x185. Edited by - kenny. on 11 Sep 2012 17:36:03 Link to comment Share on other sites More sharing options...
Stationary M25 Traveller Posted September 11, 2012 Share Posted September 11, 2012 It is maybe a factor of the tyre width and the rim width you fit them to that determines how big the overall rolling diameter is ? Link to comment Share on other sites More sharing options...
CharlesElliott Posted September 11, 2012 Share Posted September 11, 2012 Much as I like A048Rs, they aren't great in the wet (read, ****e) so for a road car something else is probably better. In a perfect world you would: - Change wheels, tyres - Reset ride height - Reset geometry - Change front wing stays for race ones - Reprogramme speedo But you can get away with just doing the first one! Link to comment Share on other sites More sharing options...
k.russell Posted September 11, 2012 Share Posted September 11, 2012 Depending what width/offset at the rear and the age of the car/ dedion bar you may need to chamfer ends slightly , also check balancing weights inside rims on front and rear. Link to comment Share on other sites More sharing options...
Ozzy Posted September 11, 2012 Share Posted September 11, 2012 Fair enough. Seems a strange way to go about things though! Link to comment Share on other sites More sharing options...
leon Posted September 11, 2012 Share Posted September 11, 2012 In simple ficticious terms consider 2 tyres, 200/60 vs.200/50 profile, both for this example on 14" wheels. The rolling radius of each is the tyre width x profile as a percentage + half the diameter of the wheel. So... 200 x 0.6 + (7x25.4mm) = 120+177.8= 197.8mm 200 x 0.5 + (177.1mm) = 100+177.8= 177.8mm So a 10% profile change for a 200 mm wide tyre gives a 20mm change in radius..... Link to comment Share on other sites More sharing options...
Tony Whitley Posted September 11, 2012 Share Posted September 11, 2012 Quoting ozzy: Fair enough. Seems a strange way to go about things though!What? Stranger than 13 inch by 185 millimetres Edited by - Tony Whitley on 11 Sep 2012 22:28:46 Link to comment Share on other sites More sharing options...
michaeljclark Posted September 11, 2012 Share Posted September 11, 2012 Toby - I've got the input codes for the post 2005 Caterham Speedo should you need them to tweak the settings for new wheel/tyre combo. Mike Link to comment Share on other sites More sharing options...
TobyCoulson Posted September 12, 2012 Author Share Posted September 12, 2012 Thanks for all the advise and offers of help. The reason I asked was after my last service it was pointed out to me that my wheels(10 spoke Anthracite 15") were showing some signs of deterioration and I thought if I was going to change the wheels at some time I might change the size. As it's not as straight forward as I had hoped I will probably wait until the tyres need changing and get new 15" rims at the same time. Now the question is what sort of rims as I don't want ones that show signs of wear after just 4 years and 5000 miles of pootling around Surrey's leafy lanes in glorious sunshine. Any recommendations but I don't want Minilites? Link to comment Share on other sites More sharing options...
peterg Posted September 12, 2012 Share Posted September 12, 2012 Toby, can't you just get your current wheels refurbed? for around £60-70 each they should come back looking like new again Link to comment Share on other sites More sharing options...
TobyCoulson Posted September 12, 2012 Author Share Posted September 12, 2012 I did think of that. A mate runs a body shop and has contacts in that sphere so I'll ask him tomorrow when I get my WRX MoTed there. Still might change the wheels just the sake of it. 😬 Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 12, 2012 Member Share Posted September 12, 2012 I had the same thought about renovation. There are several companies that are strongly recommended in the archives. Jonathan Link to comment Share on other sites More sharing options...
peterg Posted September 12, 2012 Share Posted September 12, 2012 As an aside, my ex-SWMBO was over from the US recently and hired a car from Enterprise and managed to badly kerb the left front alloy within days I Googled a mobile wheel refurb company in Catford for her (near her parents house where she was staying). They came out next day, and refurbed it to 'as new' (I really couldn't tell it wasn't a new wheel) all for £60, saving her having a lengthy argument over her deposit - the wheel refurb guy said they do a lot of hire cars now as the hire companies charge the customer for a new alloy every time they get a car returned with a kerbed wheel at £250-350 then just get the original refurbed so making around £200+ profit Link to comment Share on other sites More sharing options...
Roger Ford Posted September 12, 2012 Share Posted September 12, 2012 As it's not as straight forward as I had hoped Isn't it? What did the tyre calculator say? 195/45 R15 (as in CR500) is almost identical diameter to 185/60 R13 (as in AO48R and presumably AO21, and I think Toyos too). Link to comment Share on other sites More sharing options...
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